The present invention relates generally to oil quality sensors.
In order to prolong the life of a combustion engine, the oil which provides lubrication to the vital components within the engine must be changed before its viscosity breaks down. If the viscosity of the oil falls outside a predetermined operating range, part-to-part contact can occur and cause catastrophic failure of the engine, i.e., without proper lubrication moving parts within the engine can experience excessive wear causing the engine to become damaged.
Most oil changes today are conducted based on schedules recommended by manufacturers of the vehicles. Due to customer desire, the intervals between oil changes are getting longer. Longer intervals reduce pollution associated with the disposal of waste oil. Similarly, reducing unnecessary oil changes helps minimize pollution due to waste oil. Unfortunately, the useful life of oil, i.e., the viscosity, varies greatly depending on the quality of the oil, the age of the oil, and the operating temperature of the oil. Moreover, contamination of the oil by antifreeze or water can severely impact the oil viscosity.
As a result, the interval between oil changes may exceed the useful life of the oil and thus, it is necessary to monitor the viscosity of the oil between changes to ensure that the oil is still providing the necessary lubrication. If the viscosity of the oil deteriorates, the oil can be changed before the recommended time so that the engine will not be harmed.
Currently, there does not exist an onboard method by which the oil viscosity can relatively easily be determined. On the contrary, oil samples must be taken at certain intervals and analyzed in labs to determine the viscosity of the oil.
The present invention has recognized these prior art drawbacks, and has provided the below-disclosed solutions to one or more of the prior art deficiencies.
A method for determining oil viscosity in an engine lubrication system includes measuring an oil viscosity parameter value and then, determining the oil viscosity based thereon. Preferably, the engine lubrication system includes an engine and the oil viscosity parameter is measured while the engine is running. If an electric oil pump is used to pump oil to the engine, the oil viscosity parameter may be measured after the engine is shut down. In a preferred embodiment, the method includes generating a look-up table of oil viscosity parameter values versus viscosity values. Thereafter, the oil viscosity parameter value is compared to the look-up table in order to determine the oil viscosity. Preferably, the look-up table includes oil viscosity parameter values versus viscosity values for a range of temperatures. If the oil viscosity falls outside a predetermined operating range, a signal is sent to an output device.
In a preferred embodiment, the oil viscosity parameter value is a power consumption value of an oil pump. The look-up table that is generated includes power consumption values versus viscosity values. The power consumption value is compared to the look-up table in order to determine the oil viscosity. If a mechanical oil pump is used to pump oil to the engine, the power consumption value is determined based on a signal from a torque sensor that is mechanically coupled to the oil pump. On the other hand, if an electric oil pump is used to pump oil to the engine, the power consumption value is determined by measuring the power consumed by the pump motor.
In another aspect of the present invention, the oil viscosity parameter value is measured while pumping the oil through a bypass with the engine off. Preferably, the bypass is a calibrated capillary within the pump. In this aspect of the present invention, a look-up table is generated and includes power consumption values while the pump is pumping through the bypass.
In yet another aspect of the present invention, an engine lubrication system includes an engine and an oil pan. A pump communicates with the engine and the oil pan. The system also includes a control module that has logic means for receiving a signal that represents an oil viscosity parameter value. Moreover, the control module includes logic means for determining oil viscosity based thereon.
The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: